Install missing dependencies; set GOPATH to script directory

[ahrex]

golang and a required go crypto module were missing.

[ahrex]

Not for later versions of go.

alexander@node:~$ go version
go version go1.10.3 linux/X
alexander@node:~$ echo $GOPATH

alexander@node:~$ go env GOPATH
/home/alexander/go

[vkrasnov]

I would prefer to create a GOPATH in the working directory.

[ahrex]

Added an additional commit.